Preparation process of a porous cement-based material with electromagnetic shielding and compatible infrared protection

Abstract

The application discloses a preparation process of a porous cement-based material with electromagnetic shielding and compatible infrared protection, which comprises the following steps: (1) adding an aqueous phase into an oily phase, stirring to disperse, then performing a polymerization reaction under the conditions of heating and stirring, and then separating a solid product to obtain a spherical high-water-absorption organic polymer after washing; (2) adding the spherical high-water-absorption organic polymer into a liquid phase to soak, then adding obtained gel material into a magnetic nanoparticle dispersion medium containing a surfactant, stirring to react, and then separating a solid product, which is washed to obtain a spherical core-shell structure magnetic nanoparticle modified high-water-absorption organic polymer; and (3) adding the high-water-absorption organic polymer into a cement-based material, curing after preparing a slurry, and thus obtaining the porous cement-based material, which not only has a good electromagnetic shielding effect, but also significantly reduces heat radiation generated in an electromagnetic wave consumption process, reduces infrared detectability, and makes the cement-based material have better concealment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic shielding cement-based materials, and particularly relates to a preparation process of a porous cement-based material with electromagnetic shielding and infrared protection compatibility. BACKGROUND

[0002] Electromagnetic waves can cause electromagnetic interference, which not only seriously threatens the normal operation of equipment and the stability of communication systems, but also can be used to detect and locate equipment, so that military infrastructure and strategic target buildings face great risks of electromagnetic leakage and information leakage, which will directly endanger the political, economic and military security of a country. Traditional composite cement-based electromagnetic shielding systems absorb electromagnetic waves by adding wave-absorbing materials such as graphite and carbon powder. Although these systems have certain electromagnetic shielding effect, the high density of the wave-absorbing materials can easily increase the weight of the components or load-bearing structures. In addition, the wave-absorbing materials can also damage the cohesion of the cement stone, deteriorate the pore structure, and reduce the mechanical properties. Furthermore, the heat generated by the absorption of electromagnetic waves by the traditional composite cement-based electromagnetic shielding materials can be easily detected by infrared thermal imaging systems, which seriously affects the confidentiality of the electromagnetic protection system. SUMMARY

[0003] In view of the above problems, the present application provides a preparation process of a porous cement-based material with electromagnetic shielding and infrared protection compatibility, which forms a special small pore structure in the cement-based material by adding a high water-absorbing organic polymer modified by a magnetic nano material, not only has good electromagnetic shielding effect, but also significantly reduces the heat generated in the process of electromagnetic wave loss, reduces the infrared detectability, and makes the cement-based material of the present application have better stealth effect. Specifically, the technical scheme of the present application is as follows.

[0004] A preparation process of a porous cement-based material with electromagnetic shielding and infrared protection compatibility, comprising the following steps:

[0005] (1) The dispersion medium and the surfactant are mixed and heated and stirred to obtain an oil phase, which is ready for use.

[0006] (2) The hydrophilic polymer monomer is added to water and stirred until it is fully dissolved, then the initiator and the crosslinking agent are added and stirred uniformly to obtain an aqueous phase.

[0007] (3) The aqueous phase is added to the oil phase and stirred until it is dispersed, then a polymerization reaction is carried out under the conditions of heating and stirring, and finally the solid product is separated and washed to obtain spherical high water-absorbing organic polymer, which is ready for use.

[0008] (4) The high-spherical high-water-absorption organic polymer is added to a liquid phase for soaking, and then the water-absorption gel is added to a magnetic nanoparticle dispersion medium containing a surfactant. After stirring and reaction, the solid product is separated and washed to obtain a magnetic nanoparticle modified high-water-absorption organic polymer with a core-shell structure.

[0009] (5) The modified high-water-absorption organic polymer is added to a cement-based material to form a slurry, which is cured to obtain a porous cement-based material.

[0010] Further, in step (1), the mass ratio of the dispersion medium to the surfactant is 1-5:0.025-0.075. Optionally, the dispersion medium includes at least one of n-heptane, isooctane, cyclohexane, n-hexane, 2-methylpentane, etc. The surfactant includes at least one of silicone oil, sodium dodecyl sulfate, sodium octadecyl sulfate, Span 60, Span 80, Tween 20, Tween 60, Tween 80, etc.

[0011] Further, in step (1), the heating temperature is 30-60°C, and the stirring time is 10-30 min.

[0012] Further, in step (2), the mass ratio of the hydrophilic polymer monomer to water is 0.5-1:15-40. Optionally, the hydrophilic polymer monomer includes at least one of acrylic acid, methacrylic acid, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid, sodium vinyl sulfonate, etc.

[0013] Further, in step (2), the mass ratio of the hydrophilic polymer monomer, the initiator, and the crosslinking agent is 0.5-1:0.025-0.075:0.005-0.01.

[0014] Further, in step (2), the initiator includes at least one of potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, tert-butyl hydroperoxide, tert-butyl peroxy-2-ethylhexanoate, azobisisobutyronitrile, etc.

[0015] Further, in step (2), the crosslinking agent includes at least one of vinylmethylmethylenylsilane, divinylbenzene, vinylacrylic acid, N,N'-methylenebisacrylamide, trimethyl methacrylate, etc.

[0016] Further, in step (2), the stirring time is 10-30 min.

[0017] Further, in step (3), the mass ratio of the water phase to the oil phase is 1:2-8. Optionally, the water phase is added to the oil phase and stirred for 10-30 min.

[0018] Further, in step (3), the heating temperature is 50-100 DEG C, and the stirring time is 1-3 h. Optionally, the solid product is washed with any one of anhydrous ethanol, isopropanol, dichloromethane, diethyl ether, etc.

[0019] Further, in step (4), the mass ratio of the spherical superabsorbent organic polymer to the liquid phase is 0.5-1.1:1-5. Optionally, the liquid phase comprises any one of ammonia, white vinegar solution, water, etc. Optionally, the mass fraction of the ammonia and white vinegar solution is 10-30%.

[0020] Further, in step (4), the soaking time is 12-24 h.

[0021] Further, in step (4), the volume ratio of the water-absorbing hydrogel to the magnetic nanoparticle dispersion liquid containing a surfactant is 1:3-8. The mass ratio of the magnetic nanoparticle, surfactant, and dispersion medium is 1:0.05-0.3:2-6. Optionally, the surfactant and dispersion medium are the same as above.

[0022] Further, the magnetic nanoparticle dispersion liquid containing a surfactant is prepared by the following method: the magnetic nanoparticle is first vacuum dried and activated for 2-8 h, then dispersed into the dispersion medium and ultrasonically treated for 10-40 min. After completion, the surfactant is added, and then heated to 50-80 DEG C and stirred for 10-30 min.

[0023] Further, in step (4), the magnetic nanoparticle comprises at least one of nano-Fe3O4, nano-cobalt powder, nano-nickel powder, etc. Optionally, the particle size of the magnetic nanoparticle is 20-90 nm.

[0024] Further, in step (4), the stirring reaction time is 1-3 h. The magnetic nanomaterial utilizes a large number of hydroxyl groups on its surface to chemically bond with the hydroxyl groups on the surface of the spherical superabsorbent organic polymer, so that the magnetic nanomaterial is uniformly coated on the surface of the organic polymer to form a core-shell structure. Optionally, in step (4), the solid product is washed with any one of anhydrous ethanol, isopropanol, dichloromethane, diethyl ether, etc.

[0025] Further, in step (5), the magnetic nanoparticle modified superabsorbent organic polymer is 5-20% of the mass of the cement-based material.

[0026] Compared with the prior art, the technical scheme of the present application has at least the following beneficial effects:

[0027] The present application first prepares a spherical superabsorbent organic polymer, and then loads magnetic nanoparticles on the surface of the polymer to form a spherical core-shell structure of magnetic nanoparticle modified superabsorbent organic polymer. When the cement-based material is prepared with this electromagnetic shielding material, first, during the cement hydration stage, the spherical superabsorbent organic polymer absorbs the mixing water in the cement material to form a gel ball. As the hydration reaction continues, the water-absorbing gel ball gradually releases water, ensuring that the later hydration reaction of the cement can proceed fully, while maintaining the relative humidity inside the cement-based material, reducing the shrinkage cracking caused by self-drying, and reducing the adverse effects on the mechanical strength of the cement-based material. During the above cement hydration and hardening process, the adhesive anchoring effect of the gel product and the magnetic nanoparticles on the surface of the gel ball causes the gel ball and the magnetic nanoparticles to separate, thereby transferring the magnetic nanoparticles on the surface of the spherical superabsorbent organic polymer to the surface of the small pores, forming a special structure in which the surface of the small pores is covered with magnetic nanoparticles (see the attached drawings Figure 1 ).

[0028] When the cement-based material with the above special structure is subjected to electromagnetic wave interference, first, the spherical pores can increase the reflection and scattering times of electromagnetic waves, increasing the transmission path of electromagnetic waves, and in addition, the uniformly distributed magnetic nanoparticles on the surface of the pores have an absorption effect on electromagnetic waves, thereby effectively dissipating the electromagnetic waves. When electromagnetic waves are absorbed and converted into heat energy, due to the large specific surface area of magnetic nanomaterials, these heat can be more fully absorbed at the microscopic level, and the presence of spherical pores prevents the immediate transfer of these heat to the outside of the material, but rather stores them in these small cavities, achieving slow release of heat energy. This makes the material temperature change not too large when exerting electromagnetic shielding effect, reduces the infrared detectability of the material, enhances the concealment of the material, and can better protect military facilities.

[0029] In addition, the present application uses the spherical superabsorbent organic polymer as a carrier to uniformly distribute the easily agglomerated magnetic nanoparticles in the cement-based material, thereby maximizing the electromagnetic shielding effect, while also avoiding the problem of increased infrared detectability in the region caused by the agglomeration of magnetic nanoparticles, which consumes more electromagnetic waves and generates more heat in that region. Compared with the traditional method of directly adding magnetic nanomaterials to the cement-based material to achieve electromagnetic shielding (see the attached drawings Figure 2), the porous cement-based material of the present application not only has better electromagnetic shielding capability, avoids being penetrated by electromagnetic waves, but also overcomes the problem that the traditional electromagnetic shielding cement material is easily detected by infrared. This is because the traditional electromagnetic shielding cement material mainly relies on the absorption of electromagnetic waves by the magnetic nanomaterial distributed therein to realize the electromagnetic shielding function, but such absorption will cause heat to be generated and accumulated in the wave absorption area, and in addition, the accumulation of the magnetic nanomaterial will cause the wave absorption and heat generation to be concentrated, so that the heat in the cement-based material is more easily transmitted outward, thereby causing the surface temperature of the cement material to be significantly increased and easily detected by infrared. BRIEF DESCRIPTION OF DRAWINGS

[0030] The drawings constituting a part of the specification of the present application are used to provide further understanding of the present application, and the illustrative embodiments of the present application and the description thereof are used to explain the present application and do not constitute an improper limitation on the present application.

[0031] Figure 1 A schematic diagram of the porous cement-based material of the present application for electromagnetic shielding and infrared protection is shown in Figure 1.

[0032] Figure 2 A schematic diagram of the traditional method of adding magnetic nanomaterial directly into the cement-based material to realize electromagnetic shielding is shown in Figure 2.

[0033] Figure 3 A sample diagram of the spherical magnetic nanometer particle modified high water absorption organic polymer prepared in Example 1 below is shown in Figure 3.

[0034] Figure 4 A SEM diagram of the spherical magnetic nanometer particle modified high water absorption organic polymer prepared in Example 1 below is shown in Figure 4. DETAILED DESCRIPTION

[0035] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods not specified in the following examples are generally carried out according to the conventional conditions or according to the conditions recommended by the manufacturers.

[0036] Unless otherwise defined, all professional and scientific terms used in the present application have the same meaning as familiar to those skilled in the art. The reagents or raw materials used in the present application can be purchased through conventional channels, and unless otherwise specified, the reagents or raw materials used in the present application are used according to the conventional methods in the art or according to the product instructions.

[0037] In addition, any method and material similar or equivalent to those described can be applied in the method of the present application. The technical solutions of the present application are further described in conjunction with the drawings and specific examples in the specification.

[0038] Example 1

[0039] A process for preparing a porous cement-based material with electromagnetic shielding and compatible infrared protection, comprising the following steps:

[0040] (1) The dispersing medium (cyclohexane) and the surfactant (silicone oil) are mixed in a mass ratio of 3:0.04, heated to 60°C, and stirred for 10 min to obtain an oil phase for standby.

[0041] (2) The hydrophilic polymer monomer (acrylic acid) is mixed with water in a mass ratio of 1:40, and magnetically stirred for 25 min to fully dissolve the polymer monomer. Then the initiator (potassium persulfate) and the crosslinking agent (trimethyl methacrylate) are added and stirred for 20 min to obtain a water phase for standby. The mass ratio of the hydrophilic polymer monomer, the initiator, and the crosslinking agent is 1:0.075:0.008.

[0042] (3) The water phase of step (2) and the oil phase of step (1) are mixed in a mass ratio of 1:5, first stirred for 30 min, then heated to 70°C and stirred at this temperature for 2 h for polymerization reaction. After completion, the solid product is separated by filtration, washed with anhydrous ethanol, and dried to obtain spherical high water-absorbing organic polymer for standby.

[0043] (4) The magnetic nanoparticles (Fe3O4 with a particle size of 20-90 nm) are vacuum dried and activated at 100°C for 5 h, then added to the dispersing medium (cyclohexane) and ultrasonicated for 20 min, then the surfactant (silicone oil) is added and heated to 70°C and stirred at this temperature for 15 min to obtain a dispersion liquid for standby. The mass ratio of the magnetic nanoparticles, the surfactant, and the dispersing medium is 1:0.1:4.

[0044] (5) The spherical high water-absorbing organic polymer is soaked in 10% ammonia water for 24 h, and the mass ratio of the two is 1:2.5. Then the obtained gel material is added to the dispersion liquid (the volume ratio of the two is 1:4) and stirred for 1.5 h. After completion, the solid product is separated by filtration, washed with anhydrous ethanol, and dried to obtain a spherical core-shell structure magnetic nanoparticle modified high water-absorbing organic polymer (as shown in Figure 3 and Figure 4 ) for standby.

[0045] (6) In the 42.5 ordinary Portland cement, 10% of the spherical core-shell structure magnetic nanoparticle modified high water-absorbing organic polymer is added, then water is added according to the water-cement ratio of 0.4, and stirred at a speed of 300 rpm for 2 min. The obtained slurry is poured into a mold and naturally cured for 24 h, then demolded and placed in a standard curing room for continuous curing until the 28th day, to obtain a porous cement-based material.

[0046] The reflectivity is measured by using the bowtie method to sweep the frequency, and the test frequency range is between 2GHz and 18GHz. When the wave frequency is 2.56GHz, the reflectivity of the porous cement-based material to electromagnetic waves is -15.34dB. When the wave frequency is 17.28GHz, the reflectivity of the porous cement-based material to electromagnetic waves is -10.46dB. The temperature change of the porous cement-based material of the embodiment within 1h after absorbing electromagnetic waves is 1.5℃, which is measured by using an infrared thermal imager. The 28d compressive strength of the porous cement-based material of the embodiment is 50.6MPa, which is measured by using a universal testing machine.

[0047] Example 2

[0048] A preparation process of a porous cement-based material with electromagnetic shielding and infrared protection compatibility comprises the following steps:

[0049] (1) The dispersing medium (n-hexane) and the surfactant (sodium dodecyl sulfate) are mixed in a mass ratio of 1:0.025, heated to 40℃, and stirred for 20min to obtain an oil phase for standby.

[0050] (2) The hydrophilic polymer monomer (acrylamide) is mixed with water in a mass ratio of 0.6:25, and magnetically stirred for 10min to fully dissolve the polymer monomer. Then, the initiator (ammonium persulfate) and the crosslinking agent (N,N'-methylene bisacrylamide) are added and stirred for 10min to obtain a water phase for standby. The mass ratio of the hydrophilic polymer monomer, the initiator, and the crosslinking agent is 0.5:0.025:0.005.

[0051] (3) The water phase of step (2) and the oil phase of step (1) are mixed in a mass ratio of 1:2, stirred for 10min first, then heated to 50℃ and stirred at this temperature for 3h for polymerization reaction. After completion, the solid product is separated by filtration, washed with isopropyl alcohol, and dried to obtain spherical high-water-absorption organic polymer for standby.

[0052] (4) The magnetic nanoparticles (nanometer cobalt powder with a particle size of 20-90nm) are vacuum dried and activated at 50℃ for 8h, then added to the dispersing medium (n-hexane) and ultrasonically treated for 10min, then the surfactant (sodium dodecyl sulfate) is added, heated to 50℃ and stirred at this temperature for 30min to obtain a dispersion liquid for standby. The mass ratio of the magnetic nanoparticles, the surfactant, and the dispersing medium is 1:0.05:2.

[0053] (5) The spherical superabsorbent organic polymer is added to a white vinegar solution with a mass fraction of 30% and soaked for 18 h, and the mass ratio of the two is 0.5:1. Then the obtained gel material is added to the dispersion liquid (the volume ratio of the two is 1:3) and stirred for 1 h. After completion, the solid product is separated by filtration, washed with isopropyl alcohol, and dried to obtain a spherical core-shell structure of the magnetic nanoparticle modified superabsorbent organic polymer, which is ready for use.

[0054] (6) The magnetic nanoparticle modified spherical superabsorbent organic polymer is mixed in 42.5 Portland cement at a mass fraction of 20%, and then water is added according to a water-cement ratio of 0.5. After stirring at a speed of 100 rpm for 5 min, the obtained slurry is poured into a mold and naturally cured for 24 h. After demolding, it is placed in a standard curing room for continuous curing until the 28th day, and a porous cement-based material is obtained.

[0055] The reflectivity is measured by using the bowtie method to sweep the frequency, and the frequency range is between 2 GHz and 18 GHz. At a wave frequency of 2.56 GHz, the reflectivity of the porous cement-based material of the embodiment to electromagnetic waves is -17.84 dB. At a wave frequency of 17.28 GHz, the reflectivity of the porous cement-based material to electromagnetic waves is -11.75 dB. The temperature change of the porous cement-based material of the embodiment within 1 h after absorbing electromagnetic waves is 1.3°C, which is measured by using an infrared thermal imager. The 28d compressive strength of the porous cement-based material of the embodiment is 45.8 MPa, which is measured by using a universal testing machine.

[0056] Example 3

[0057] A preparation process of a porous cement-based material with electromagnetic shielding and infrared protection compatibility, comprising the following steps:

[0058] (1) The dispersion medium (n-heptane) and the surfactant (span 60) are mixed according to a mass ratio of 1:0.075, heated to 30°C, and stirred for 30 min to obtain an oil phase for standby use.

[0059] (2) The hydrophilic polymer monomer (methyl methacrylate) is mixed with water according to a mass ratio of 0.5:15, and magnetically stirred for 10 min to make the polymer monomer fully dissolved. Then the initiator (azobisisobutyronitrile) and the crosslinking agent (divinylbenzene) are added and stirred for 30 min to obtain an aqueous phase for standby use. The mass ratio of the hydrophilic polymer monomer, the initiator, and the crosslinking agent is 0.75:0.06:0.01.

[0060] (3) The water phase of step (2) and the oil phase of step (1) are mixed in a mass ratio of 1:8, stirred for 30 min, heated to 100℃ and stirred at this temperature for 1 h to carry out the polymerization reaction. After completion, the solid product is separated by filtration, washed with dichloromethane and dried to obtain spherical superabsorbent organic polymers, which are ready for use.

[0061] (4) The magnetic nanoparticles (nano nickel powder with a particle size of 20-90 nm) are vacuum dried and activated at 80℃ for 2 h, then added to a dispersion medium (n-heptane) and ultrasonically treated for 40 min, then a surfactant (span 60) is added, heated to 80℃ and stirred at this temperature for 10 min to obtain a dispersion ready for use. The mass ratio of the magnetic nanoparticles, surfactant and dispersion medium is 1:0.3:6.

[0062] (5) The spherical superabsorbent organic polymers are soaked in water for 12 h, and the mass ratio of the two is 1.5:5. Then the obtained gel material is added to the dispersion (the volume ratio of the two is 1:8) and stirred for 3 h. After completion, the solid product is separated by filtration, washed with anhydrous ethanol and dried to obtain core-shell type magnetic nanoparticle modified spherical superabsorbent organic polymers, which are ready for use.

[0063] (6) 5% of the magnetic nanoparticle modified spherical superabsorbent organic polymers by mass are added to 42.5 Portland cement, then water is added according to a water-cement ratio of 0.35, and stirred at a speed of 200 rpm for 3 min. The obtained slurry is poured into a mold and naturally cured for 24 h, then demolded and placed in a standard curing room for continuous curing until the 28th day, to obtain a porous cement-based material.

[0064] The reflectivity is measured by using the bowtie method to sweep the frequency, and the frequency range is between 2 GHz and 18 GHz. At a wave frequency of 2.56 GHz, the reflectivity of the porous cement-based material of the embodiment to electromagnetic waves is -14.12 dB. At a wave frequency of 17.28 GHz, the reflectivity of the porous cement-based material to electromagnetic waves is -9.15 dB. The temperature change of the porous cement-based material of the embodiment within 1 h after absorbing electromagnetic waves is 2.2℃, measured by an infrared thermal imager. The 28d compressive strength of the porous cement-based material of the embodiment is 52.3 MPa, measured by a universal testing machine.

[0065] Example 4

[0066] A preparation process of an electromagnetic shielding porous cement-based material, comprising the following steps:

[0067] A mixture of 10% by mass of magnetic nanoparticles (Fe3O4 with a particle size of 20~90nm) and spherical superabsorbent organic polymer (prepared in step (3) of Example 1 above) was added to 42.5 ordinary Portland cement (the mass ratio of the two is 1:0.784). Then, water was added at a water-cement ratio of 0.4 and stirred at a speed of 300rpm for 2min. The resulting slurry was poured into a mold and naturally cured for 24h. After demolding, it was placed in a standard curing room and continued to be cured until the 28th day, thus obtaining a porous cement-based material.

[0068] The reflectivity was measured using the arc-shaped frequency sweep method, with a test frequency range between 2 GHz and 18 GHz. At a wave frequency of 2.56 GHz, the reflectivity of the porous cement-based material in this embodiment to electromagnetic waves was -7.2 dB. At a wave frequency of 17.28 GHz, the reflectivity was -3.5 dB. The temperature change of the porous cement-based material in this embodiment within 1 hour after absorbing electromagnetic waves was measured to be 2.5 °C using an infrared thermal imager. The 28-day compressive strength of the porous cement-based material in this embodiment was measured to be 44.8 MPa using a universal testing machine.

[0069] Example 5

[0070] A process for preparing an electromagnetically shielded porous cement-based material includes the following steps:

[0071] (1) Magnetic nanoparticles (cobalt nanoparticles with a particle size of 20~90nm) were vacuum dried and activated at 50℃ for 8h, then added to a dispersion medium (n-hexane) and sonicated for 10min. Then, a surfactant (sodium dodecyl sulfate) was added, and the mixture was heated to 50℃ and stirred at that temperature for 30min to obtain a dispersion for later use. The mass ratio of the magnetic nanoparticles, surfactant and dispersion medium was 1:0.05:2.

[0072] (2) Commercially available water-absorbing resin (model B20, Renqiu Quanxing Chemical Co., Ltd.) was added to a 30% (w / w) white vinegar solution and soaked for 18 hours. The mass ratio of the two was 0.5:1. Then, the obtained gel material was added to the dispersion (volume ratio of the two was 1:3) and stirred for 1 hour. After the reaction was completed, the solid product was filtered off, washed with isopropanol and dried to obtain magnetic nanoparticle modified water-absorbing resin for later use.

[0073] (3) Add 20% by weight of the nanoparticle modified water-absorbing resin described in this embodiment to 42.5 ordinary Portland cement, then add water at a water-cement ratio of 0.5 and stir at 100 rpm for 5 minutes. Pour the resulting slurry into a mold and cure naturally for 24 hours. After demolding, place it in a standard curing room and continue curing until the 28th day to obtain a porous cement-based material.

[0074] The reflectivity of the porous cement-based material of the embodiment is -9.67 dB to electromagnetic waves at a wave frequency of 2.56 GHz. The reflectivity of the porous cement-based material to electromagnetic waves is -5.12 dB at a wave frequency of 17.28 GHz. The temperature change of the porous cement-based material of the embodiment within 1 h after absorbing electromagnetic waves is 12.6 ℃, which is measured by an infrared thermal imager. The 28 d compressive strength of the porous cement-based material of the embodiment is 24.6 MPa, which is measured by a universal testing machine.

[0075] Example 6

[0076] A preparation process of an electromagnetic shielding porous cement-based material, comprising the following steps:

[0077] (1) The magnetic nano-particles (nano-nickel powder with a particle size of 20-90 nm) are vacuum dried and activated at 80 ℃ for 2 h, then added to a dispersion medium (n-heptane) and ultrasonically treated for 40 min, then a surfactant (Span 60) is added and heated to 80 ℃ and stirred at the temperature for 10 min to obtain a dispersion liquid for standby use. The mass ratio of the magnetic nano-particles, the surfactant and the dispersion medium is 1:0.3:6.

[0078] (2) The commercially available water-absorbing resin (model JB40-80, produced by Renqiu Quanxing Chemical Co., Ltd.) is soaked in water for 12 h, and the mass ratio of the two is 1.5:5. Then the obtained gel material is added to the dispersion liquid (the volume ratio of the two is 1:8) and stirred for 3 h, and after completion, the solid product is separated by filtration, washed with anhydrous ethanol and dried to obtain the magnetic nano-particle modified water-absorbing resin for standby use.

[0079] (6) The magnetic nano-particle modified water-absorbing resin is added to 42.5 ordinary Portland cement at a mass ratio of 5%, then water is added according to a water-cement ratio of 0.35, and stirred at a speed of 200 rpm for 3 min. The obtained slurry is poured into a mold and naturally cured for 24 h, then demolded and placed in a standard curing room for curing until the 28th day, to obtain the porous cement-based material.

[0080] The reflectivity is measured by using the bowtie method for frequency sweep, and the test frequency range is between 2 GHz and 18 GHz. The reflectivity of the porous cement-based material of the embodiment to electromagnetic waves is -5.4 dB at a wave frequency of 2.56 GHz. The reflectivity of the porous cement-based material to electromagnetic waves is -1.7 dB at a wave frequency of 17.28 GHz. The temperature change of the porous cement-based material of the embodiment within 1 h after absorbing electromagnetic waves is 18.5 ℃, which is measured by an infrared thermal imager. The 28 d compressive strength of the porous cement-based material of the embodiment is 29.3 MPa, which is measured by a universal testing machine.

[0081] Example 7

[0082] A preparation process of a porous cement-based material with electromagnetic shielding and compatible infrared protection, comprising the following steps:

[0083] (1) The spherical superabsorbent organic polymer (the same as in the above embodiment 2) is directly added to the dispersion liquid (the same as in the above embodiment 2) and stirred for 1h, and the mass ratio of the spherical superabsorbent organic polymer to the dispersion liquid is 1:3. After completion, the solid product is separated by filtration, washed with isopropanol and dried, to obtain a core-shell type magnetic nanoparticle modified spherical superabsorbent organic polymer, which is ready for use.

[0084] (2) The magnetic nanoparticle modified spherical superabsorbent organic polymer is mixed with 20% of the mass of the 42.5 ordinary Portland cement, and then water is added according to a water-cement ratio of 0.5 and stirred at a speed of 100 rpm for 5 min. The obtained slurry is poured into a mold and naturally cured for 24h, and then demolded and placed in a standard curing room for further curing until the 28th day, to obtain a porous cement-based material.

[0085] The reflectivity is measured by using the bowtie method to sweep the frequency, and the frequency range is between 2GHz and 18GHz. When the wave frequency is 2.56 GHz, the reflectivity of the porous cement-based material of the embodiment to electromagnetic waves is -7.72dB. When the wave frequency is 17.28 GHz, the reflectivity of the porous cement-based material to electromagnetic waves is -3.48dB. The infrared thermal imager is used to measure the temperature change of the porous cement-based material of the embodiment within 1h after absorbing electromagnetic waves, and the temperature change is 1.9℃. The universal testing machine is used to measure the 28d compressive strength of the porous cement-based material of the embodiment, and the compressive strength is 45.6MPa.

[0086] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a porous cementitious material for electromagnetic shielding and compatible infrared protection, characterized by, The method comprises the following steps: (1) After mixing the dispersion medium and the surfactant, heating and stirring are performed to obtain an oil phase, which is ready for use; the mass ratio of the dispersion medium and the surfactant is 1-5:0.025-0.075; (2) Hydrophilic polymer monomers are added to water and stirred until fully dissolved, then an initiator and a crosslinking agent are added, and after uniform stirring, an aqueous phase is obtained; the mass ratio of the hydrophilic polymer monomers to water is 0.5-1:15-40; the mass ratio of the hydrophilic polymer monomers, the initiator and the crosslinking agent is 0.5-1:0.025-0.075:0.005-0.01; the hydrophilic polymer monomers include at least one of acrylic acid, methacrylic acid, acrylamide, 2-acrylamide-2-methylpropanesulfonic acid and sodium vinyl sulfonate; (3) The aqueous phase is added to the oil phase in a mass ratio of 2:8 and stirred until dispersed, then polymerization is performed under heating and stirring, and after completion, a solid product is separated out, washed and then spherical superabsorbent organic polymers are obtained, which are ready for use; (4) The spherical superabsorbent organic polymers are soaked in a liquid phase, then the obtained gel material is added to a dispersion medium of magnetic nanoparticles containing a surfactant, and after stirring and reaction, a solid product is separated out, washed and then spherical core-shell structure magnetic nanoparticle modified superabsorbent organic polymers are obtained; the volume ratio of the gel material to the dispersion liquid of magnetic nanoparticles containing a surfactant is 1:3-8; the mass ratio of the magnetic nanoparticles, the surfactant and the dispersion medium is 1:0.05-0.3:2-6; the dispersion liquid of magnetic nanoparticles containing a surfactant is prepared by the following method: the magnetic nanoparticles are vacuum dried and activated for 2-8 hours, then dispersed in the dispersion medium and ultrasonically treated for 10-40 minutes; after completion, the surfactant is added, then heated to 50-80 DEG C and stirred for 10-30 minutes; the magnetic nanoparticles include at least one of nano Fe3O4, nano cobalt powder and nano nickel powder; (5) The magnetic nanoparticle modified superabsorbent organic polymers are added to a cement-based material, a slurry is prepared and then cured, and then a porous cement-based material is obtained.

2. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (1), the dispersion medium includes at least one of n-heptane, isooctane, cyclohexane, n-hexane, isobutane, methane and n-butane.

3. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (1), the surfactant includes at least one of silicone oil, sodium dodecyl sulfate, sodium octadecyl sulfate, Span 60, Span 80, Tween 20, Tween 60 and Tween 80.

4. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (1), the heating temperature is 30-60 DEG C, and the stirring time is 10-30 minutes.

5. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (2), the initiator includes at least one of potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, tert-butyl hydroperoxide, tert-butyl peroxy-2-ethylhexanoate and azobisisobutyronitrile.

6. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (2), the crosslinking agent includes at least one of vinyl methyl oxy vinyl silane, divinyl benzene, vinyl acrylic acid, N,N'-methylene bisacrylamide and trimethyl methacrylate.

7. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (2), the stirring time is 10-30 min.

8. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, After adding the aqueous phase to the oil phase, stirring is performed for 10-30 min.

9. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (3), the heating temperature is 50-100℃, and the stirring time is 1-3 h.

10. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (3), the solid product is washed with any one of anhydrous ethanol, isopropanol, dichloromethane, and diethyl ether.

11. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the mass ratio of the spherical superabsorbent organic polymer to the liquid phase is 0.5-1.1:1-5.

12. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the liquid phase includes any one of ammonia, white vinegar solution, and water.

13. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 12, characterized in that, In step (4), the mass fraction of the ammonia and white vinegar solution is 10-30%.

14. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the soaking time is 12-24 h.

15. The process for the preparation of a multi-porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the dispersion medium includes at least one of n-heptane, isooctane, cyclohexane, n-hexane, isobutane, methane, and n-butane.

16. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the surfactant includes at least one of silicone oil, sodium dodecyl sulfate, sodium octadecyl sulfate, Span 60, Span 80, Tween 20, Tween 60, and Tween 80.

17. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the particle size of the magnetic nanoparticles is 20-90 nm.

18. The process for the preparation of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to claim 1, characterized in that, In step (4), the stirring reaction time is 1-3 h.

19. The process for the preparation of a porous cement-based material electromagnetically shielding and compatible with infrared protection according to claim 1, characterized in that, In step (4), the solid product is washed with any one of anhydrous ethanol, isopropanol, dichloromethane, and diethyl ether.

20. Process for the production of a porous cement-based material for electromagnetic shielding and compatible infrared protection according to any one of claims 1-9, characterized in that, In step (5), the mass fraction of the modified superabsorbent organic polymer of the magnetic nanoparticles in the cement-based material is 5-20%.

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